1. Field of the Invention
The present invention relates to wireless data-collection terminals, and more particularly, to the association of a wireless bar code scanner to a base station without physical contact between the wireless scanner and the base station.
2. Description of Related Art
In the automated identification and data capture industry, it is known to operate a wireless local area network (LAN) that includes a plurality of handheld data-collection terminals that communicate over a radio frequency (RF) channel with a central host computer. The data-collection terminals enable an operator to scan and decode data that may be encoded in the form of a one or two-dimensional bar code symbology. The decoded information is then transmitted back to the host across the RF channel. Such wireless LAN systems are particularly well suited to data capture applications as diverse as process and inventory control, time and attendance monitoring, security management, customer service and point of sale recording, shipping and receiving record keeping, and warehouse operations.
The wireless LAN may further include one or more printers for producing bar code labels used in identifying items that are tracked in a particular data capture application. To achieve maximum data throughput, dedicated thermal printers are generally coupled directly to the central host computer through a hard-wired communication link. The printers may further be located in a climate controlled environment that is otherwise isolated from the rest of the LAN.
From time to time, it becomes necessary for a wireless data-collection terminal to communicate directly to a printer or to a computer terminal in one or more wireless networks. For example, a test batch configuration may be stored in memory within a data-collection terminal and loaded directly into one or more printers to insure uniform print results (referred to as "cloning"). Alternatively, an operator of a data-collection computer in a large facility may wish to utilize a local printing station disposed in near proximity to a work location rather than returning to a central printing station adjacent to the central host computer. In these situations, the operator must establish a communications link between the data-collection terminal and the printer or computer terminal in the wireless network. This can be accomplished using conventional cables having standard interface connectors, e.g., an RS-232 connector on a printer cable, which allows for communications between the two devices across the cable.
Despite the advantages of coupling the data-collection terminal directly to the printer, there are numerous operational difficulties that make such a connection impractical. For example, the physical connection across the cable greatly reduces the operational range of the data-collection terminal. In addition, repeated connection and disconnection of interface cables tends to weaken the connectors of the two devices resulting in intermittent electrical connections.
Even more significant is the threat of harm to either of the printer or the data-collection terminal due to effects such as electro-static discharge (ESD) or electromagnetic interference (EMI). ESD refers to sparks or electrons that jump from an electrically charged object to an approaching conductive object. EMI refers to electromagnetic waves that emanate from an electrical device, including both low-frequency waves from electromechanical devices and high-frequency waves (RFI) from electronic circuit chips and other electronic devices. Any ESD which results from the coupling of the interface cable between the printer and the data-collection computer can damage the delicate electronic circuitry of either of the two systems. Moreover, EMI from an unshielded or poorly shielded interface cable can interfere with the operation of the printer or the data-collection computer, resulting in further damage or degradation of system performance.
To retain portability and resolve other of the above problems, it is known in the art to establish a wireless communications link between the data-collection terminal and the printer or computer terminal of the wireless network. A prior art system for "associating" a wireless scanner with a computer terminal is illustrated in FIG. 1. The system includes a host computer 10, a wedge 18 and a data-collection terminal 20, which is a conventional wireless scanner. A keyboard 14 is provided for user input and is connected to the host computer 10 through a cable 16.
The wedge 18 is connected to the cable 16, between the keyboard 14 and the computer 10. The wedge 18 includes a receiving cavity 22 and an antenna 26 which is used for wireless communication over an RF channel with the wireless scanner 20. The wireless scanner 20 includes an antenna 28 and has a bottom portion 26 adapted to engage the receiving cavity 22 of the wedge 18.
In operation, the wireless scanner 20 cannot communicate with the host computer 10 until a communications link is established between the wireless scanner 20 and the wedge 18. This requires both the wireless scanner 20 and the wedge 18 to utilize the same protocol, RF channels, etc. To establish such a link, the user inserts the bottom portion 26 of the scanner into the receiving cavity 22 of the wedge 18. The bottom portion 26 and the receiving cavity 22 include mating electrical connections (not shown), through which initial communications between the two devices are conducted.
The wedge 18 senses that the wireless scanner 20 has been inserted into the cavity 22 and seeks authorization from the computer 10 to establish a wireless communications link. If the computer 10 allows the wireless scanner 20 to join in the wireless network the wedge 18 sends information to the scanner 20 regarding frequency, protocol, unique IDs and any other information needed to establish communications. The wireless scanner 20 stores this information and can then be removed from the wedge 18 and used anywhere within range of the antenna 26. When a printed bar code symbol is scanned and decoded by the wireless scanner 20, the decoded information is transmitted from the wireless scanner 20 through the antenna 28, and the decoded information is received at the wedge 18 through antennae 24 where it is used as input for the host computer 10.
The prior art system of FIG. 1 has many drawbacks. For example, repeated physical connection between the wireless scanner 20 and the wedge 18 can result in wear of the connecting parts. Further, because a physical connection is required to associate the wireless scanner 20 to the wedge 18, ESD and EMI are still a problem. Another drawback is that a user must locate the wedge 18 which may be inconveniently located in a work area. Multiple wedges could be placed throughout the work area making them more accessible, but this requires additional hardware and wiring, making the wireless network more expensive and more complex.